FIELD OF THE INVENTION
[0001] This invention in general relates to three-phase power devices (such as three-phase
motors) and, more particularly, to a switching circuit mounted on a printed circuit
board having embedded directional impedance control channels.
BACKGROUND OF THE INVENTION
[0002] A three-phase motor (such as a permanent magnet synchronous motor and induction motor)
is used in automotive applications such as power steering systems. It is known to
control the phase windings in a three-phase motor using pulse width modulated signals.
The pulse width modulated signals are applied to an inverter or a series of switching
devices that connect the phase windings of the motor to either a positive or negative
(ground) terminal of the vehicle battery.
[0003] In particular, a series of switching devices are usually part of a switching circuit
that drive the three-phase motor. A current sensor is used to help determine and track
the voltages being applied to each phase winding of the motor. In the past, the switching
circuit and current sensor have been mounted on a ceramic substrate. A series of wire
bonds are used to interconnect the switching devices and components. The use of wire
bonds and a ceramic substrate, however, is expensive and there is a need for less
expensive materials and designs.
[0004] It would be beneficial to use a printed circuit board to mount and interconnect the
switching devices, such as a printed circuit board made of an epoxy glass known as
FR4. This would allow a manufacturer to use a Field Effect Transistor (FET) in the
form of a surface mounted power device. It would also be beneficial to eliminate the
need of wire bonds. This would reduce the cost of implementing the system by eliminating
cycle time, factory automation equipment, and maintenance cost associated with traditional
wire bond methods.
[0005] It has been found, however, that applying a system to a printed circuit board generates
problems. For instance, a system that applies sinusoidal drive signals to a three-phase
motor is subject to a phenomenon known as torque ripple. Torque ripple can be characterized
as harmonics (distortion) in the sinusoidal motor drive voltages that are created
when the voltage loss from phase to phase is not balanced. These torque ripple harmonics
generate undesirable problems. For instance, consider a three-phase motor used in
a power steering application in an automobile. A driver of the automobile will feel
any torque ripple harmonics in the form of small but repetitive oscillations while
turning the steering wheel. This is an undesirable condition to automobile drivers
and a need exists for eliminating, or at least substantially reducing, the effect
of torque ripple harmonics.
[0006] Accordingly, a need exists to reduce the cost of implementing a three-phase control
system yet solves other problems associated with torque ripple harmonics. The present
invention addresses ways to solve this need. In particular, the present invention
solves the problem of torque ripple harmonics when applying the three-phase motor
control circuitry in a printed circuit board layout. This is accomplished by providing
a mechanism to optimize, or otherwise balance, the resistive and reactive impedances
that occur when applying the three-phase motor control circuitry in a printed circuit
board layout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 is a diagram of a system that could utilize the embodiments of the present
invention, the system having a power source, an inverter or switching circuit, and
a three-phase motor;
FIG. 2 is a diagram of a controller for the system in FIG. 1 for generating signals
to a plurality of switching devices;
FIG. 3 is a table reflecting the eight possible switching states for a three-phase
power device;
FIG. 4 is top view of one embodiment of a switching circuit and current sensor mounted
on a printed circuit board;
FIG. 5 is top view of one embodiment of an embedded second layer of the printed circuit
board in FIG. 4;
FIG. 6 is top view of one embodiment of a switching circuit and current sensor mounted
on a printed circuit board; and
FIG. 7 is top view of one embodiment of an embedded third layer of the printed circuit
board in FIG. 6.
FIG. 8 is top view of another embodiment of a switching circuit and current sensor
mounted on a printed circuit board;
FIG. 9 is top view of another embodiment of an embedded second layer of the printed
circuit board in FIG. 8;
FIG. 10 is top view of another embodiment of a switching circuit and current sensor
mounted on a printed circuit board; and
FIG. 11 is top view of another embodiment of an embedded third layer of the printed
circuit board in FIG. 10.
[0009] While the invention is susceptible to various modifications and alternative forms,
specific embodiments have been shown by way of example in the drawings and will be
described in detail herein. However, it should be understood that the invention is
not intended to be limited to the particular forms disclosed. Rather, the invention
is to cover all modifications, equivalents and alternatives falling within the spirit
and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION
[0010] What is described is a design for implementing a switching circuit for a three-phase
power device on a printed circuit board. The present invention uses embedded directional
impedance control channels to balance the resistive and reactive impedance that occur
when applying the switching circuit in a printed circuit board application. For purposes
of illustration and description, an example of an application for a three-phase motor
for automotive uses will be used. Three-phase motors, such as permanent magnet synchronous
motors, may be used as part of a power steering system in an automobile. The present
invention, however, is not limited to three-phase motors for automobiles and may be
applicable to other three-phase devices.
[0011] To this end, generally, there is a printed circuit board for a three-phase power
device. The printed circuit board has a first switching device, a second switching
device, a third switching device, and a common source node that are each mounted to
a surface of the printed circuit board. The printed circuit board further includes
at least a first set of conductive paths in a first layer, a second set of conductive
paths in a second layer, and a plurality of vias that connects the first layer to
the second layer. The first set of conductive paths provides electrical conductivity
between the common source node, the first switching device, the second switching device,
and third switching device. The second set of conductive paths in the second layer
provide electrical conductivity between the common source node, the first switching
device, and the third switching device. In this embodiment, the physical distance
between the first low side switching device and the common source node and the distance
between the third low side switching device and the common source node is greater
than a distance between the second low side switching device and the common source
node.
[0012] The present invention may be applied to a set of low side switching device and/or
to a set of high side switching devices. Accordingly, in one embodiment, the switching
devices are low side switching devices and the common source node may include a current
sensor. In another embodiment, the switching devices are high side switching devices
and the common source node may include a power source node.
[0013] In a further embodiment, there is a printed circuit board for a three-phase power
device that has at least a first low side switching device, a second low side switching
device, a third low side switching device, and a current sensor that are each mounted
to a surface of the printed circuit board. The printed circuit, in one embodiment,
has a first set of conductive paths in a first layer, a second set of conductive paths
in a second layer, and a plurality of vias. The first set of conductive paths in the
first layer of the printed circuit board provides electrical conductivity between
the low side switching devices and the current sensor. The second set of conductive
paths in the second layer of the printed circuit board provides electrical conductivity
between the first low side switching device and the third low side switching device
and the current sensor. The plurality of vias connect the first layer to the second
layer of the printed circuit board. In this embodiment, the physical distance between
the first low side switching device and the current sensor and the distance between
the third low side switching device and the current sensor is greater than a distance
between the second low side switching device and the current sensor. The printed circuit
board may further have a third set of conductive paths in a third layer and a second
plurality of vias. The third set of conductive paths in the third layer provides electrical
conductivity between the first low side switching device and the third low side switching
device.
[0014] In another embodiment, there is a printed circuit board for a three-phase power device
having a switching circuit and a current sensor mounted on a surface of the printed
circuit board. The switching circuit has three sets of switching devices where each
set includes a high side switching device and a low side switching device. The printed
circuit board comprises a first set of conductive paths in a first layer, a second
set of conductive paths in a second layer, and a plurality of vias. The first set
of conductive paths in the first layer of the printed circuit board provides electrical
conductivity between each of the low side switching devices in the switching circuit
and the current sensor. The second set of conductive paths in the second layer of
the printed circuit board provides electrical conductivity between at least two of
the low side switching devices of the switching circuit and the current sensor. The
plurality of vias connects the first layer of the printed circuit board to the second
layer of the printed circuit board. The second conductive paths assist in substantially
balancing impedances between the low side switching devices of the switching circuit
and the current sensor. The printed circuit board may further have a third set of
conductive paths in a third layer and a second plurality of vias. The third set of
conductive paths in the third layer provides electrical conductivity between at least
two of the low side switching devices of the switching circuit.
[0015] There is also a printed circuit board for a three-phase power device that has at
least a first low side switching device, a second low side switching device, a third
low side switching device, and a current sensor, each mounted to a surface of the
printed circuit board. Here, the printed circuit board comprises a first set of conductive
paths in a first layer, a second set of conductive paths in a second layer, a third
set of conductive paths in a third layer, and a first and second set of vias. The
first set of conductive paths in the first layer of the printed circuit board provides
electrical conductivity between the low side switching devices and the current sensor.
The second set of conductive paths in the second layer of the printed circuit board
provides electrical conductivity between the first low side switching device, the
third low side switching device and the current sensor. The third set of conductive
paths in the third layer of the printed circuit board provides electrical conductivity
between the first low side switching device and the third low side switching device.
The first set of vias connect the first layer of the printed circuit board to the
second layer of the printed circuit board. The second set of vias connect the first
layer of the printed circuit board'to the third layer of the printed circuit board.
[0016] In yet another embodiment, there is a printed circuit board that has a power source
node, a first high side switching device, a second high side switching device, and
a third high side switching device that are each mounted on the printed circuit board.
The printed circuit board further includes at least a first set of conductive paths
in a first layer, a second set of conductive paths in a second layer, and a plurality
of vias that connect the first layer to the second layer. Here, the first set of conductive
paths in the first layer provide electrical conductivity between the power source
node, the first high side switching device, the second high side switching device,
and the third high side switching device. The second set of conductive paths in the
second layer provide electrical conductivity between the power source node, the first
high side switching device, and the third high side switching device. The physical
distance between the power source node and the first high side switching device and
the distance between the power source node and the third high side switching device
is greater than a distance between the power source node and the second high side
switching device.
[0017] Now, turning to the drawings, an example use of a system for a three-phase motor
in an automotive application will be explained. Referring to FIG. 1, there is a system
20 having generally a power source 22, an inverter or switching circuit 24, a current
sensor 26, and a motor 28. For automotive use, the power source 22 may be an automobile
DC battery having a positive terminal 30 and a negative terminal 32. The negative
terminal 32 may also be a ground connection. The motor 28 may be a motor having three
phase windings A, B, C in a star connection, although other connection types may be
used such as a delta connected motor. Such motors may include, for example, a permanent
magnet synchronous motor or an induction motor.
[0018] The inverter or switching circuit 24 and the current sensor may be mounted on a surface
of a printed circuit board, as will be explained in more detail below. The inverter
or switching circuit 24 includes three sets of switching devices, one set for each
phase winding of the motor 28. A first set of switching devices S1, S2 are capable
of providing a first voltage V
a to the first phase winding A. A second set of switching devices S3, S4 are capable
of providing a second voltage V
b to the second phase winding B. A third set of switching devices S5, S6 are capable
of providing a third voltage V
c to the third phase winding C.
[0019] In one embodiment, each set of switching devices has a high side switching device
S1, S3, S5 connected to the positive terminal 30 of the power source 22 and a low
side switching device S2, S4, S6 connected to the negative terminal 32 of the power
source 22 (or a ground connection). Each switching device within a set is complimentary
to the other switch within the same set. For example, when the high side switching
device S1 of the first set of switching devices S1, S2 is closed, the corresponding
low side switching device S2 within the first set of switching devices S1, S2 is open.
Similarly, when the high side switching device S1 of the first set of switching devices
S1, S2 is open, the corresponding low side switching device S2 within the first set
of switching devices S1, S2 is closed.
[0020] By having complementary switching devices, the opening and closing of switching devices
within each set allows each phase winding A, B, C of the motor 28 to be connected
to a positive terminal 30 or a negative terminal 32 (or ground) of the power supply
22. This permits a voltage V
a, V
b, or V
c to be applied to a corresponding phase winding A, B, or C of the motor 28, respectively.
The current flowing through each phase winding A, B, or C is represented in FIG. 1
by a corresponding variable i_a, i_b, or i_c, respectively.
[0021] As will be explained in more detail below, in one embodiment, the switching devices
S1-S6 may be field effect transistors (FETs), each having a source terminal, a drain
terminal, and a gate terminal. The FET can be used as a switch by raising and lowering
the voltage applied to the gate terminal above and below a threshold value. Applying
a voltage above a threshold value will allow current to pass through a switching device
S1-S6. Other suitable types of devices exist for the switching devices S1-S6 such
as power transistors like IGBT, power MOSFET, and bipolar.
[0022] Pulse width modulated (PWM) signals may be used to control the switching devices
S1-S6. Referring to FIG. 2, a controller 36 is used to generate a PWM signal to each
of the switching devices S1-S6. The controller 36 generates the PWM signal based on
the current measurements provided by the current sensor 26. The controller 36 may
include a digital processor and memory to store software having control algorithms.
The digital processor supplies the PWM signals based the control algorithms implemented
in software. A suitable controller 36 may include a DSP processor and memory (not
shown).
[0023] Referring back to FIG. 1, to adequately control the motor 28, the currents for variables
i_a, i_b, i_c need to be measured or otherwise known. In one embodiment, the current
sensor 26 is positioned on the DC link between the power supply 22 and the switching
circuit 24. In particular, the current sensor 26 is located between the low side switching
devices S2, S4, S6 of the switching circuit 24 and the negative terminal 30 of the
power supply 22. The current sensor 26 may also be positioned between the low side
switching devices S2, S4, S6 of switching circuit 24 and a ground connection. In either
event, the current sensor 26 is electrically connected to the low side switching devices
S2, S4, S6 of the switching circuit 24. The present invention is directed to balancing
the resistive and reactive impedances in this electrical connection when the switching
circuit 24 and the current sensor 26 are implemented on, or mounted to, a surface
of a printed circuit board.
[0024] The current sensor 26 may be a sensor that measures the voltage drop across a resistor.
The current sensor 26 may be capable of converting the measured voltage drop to a
current (represented by i_de_link) through the DC link according to well-known methods.
Alternatively, the measured voltage drop from sensor 26 may be provided to the controller
36 and the controller 36 may convert the sensed voltage drop to a current.
[0025] As explained above, each switching device within a set of switching devices is complementary
to the other switching device. For a three-phase motor system, this results in eight
possible switching states. The table illustrated in FIG. 3 reflects the eight possible
switching states as vectors V0-V7. The first column 40 in the table represents the
states (open/closed) of the first set of switching devices S1, S2. The second column
42 in the table represents the states (open/closed) of the second set of switching
devices S3, S4. The third column 44 in the table represents the states (open/closed)
of the third set of switching devices S5, S6. The fourth column 46 reflects the relationship
between the current through the DC link (i_dc_link) and the currents i_a, i_b, and
i_c through the various phase windings A, B, and C. The fifth column 48 reflects the
eight vector states. Out of the eight possible switching states, there are six active
vector states (V1-V6) where current will flow through the DC link and two zero vector
states (V0, V7) where no current will flow through the DC link.
[0026] As mentioned above, the application of sinusoidal drive voltages to a three-phase
power device, such as a motor, is subject to torque ripple harmonics. The problem
of torque ripple harmonics needs to be addressed when attempting to implement the
switching circuit 24 and the current sensor 26 in a printed circuit board layout.
It has been found that torque ripple harmonics will result when resistive and reactive
impedances are not balanced. The present invention addresses ways to eliminate, or
at least substantially reduce, the effect of the torque ripple harmonics.
[0027] Referring to FIG. 4, there is shown a printed circuit board 50 for a three-phase
power device, such as the motor 28 described above. The printed circuit board 50 has
a switching circuit 24 and a current sensor 26 mounted on a surface 52 of the printed
circuit board 50. The switching circuit 24 has three sets of switching devices. Each
set of switching devices has a high side switching device S1, S3, S5 and a low side
switching device S2, S4, S6.
[0028] In this embodiment, the positive terminal 30 of the power source 22 is connected
to the high side switching devices S1, S3, S5 through a power supply conductive pad
54. The power supply conductive pad 54 may actually supply power to the high side
switching devices S1, S3, S5 through multiple layers in the printed circuit board.
This may be important if the current required to drive the three-phase power device
is relatively high. The multiple layers may be electrically tied together through
vias (not shown).
[0029] Each set of switching devices is connected to each other through a series of interconnecting
pads 56A, 56B, 56C. For instance, a first interconnecting pad 56A provides electrical
contact between a first high side switching device S1 and a first low side switching
device S2. A second interconnecting pad 56B provides electrical contact between a
second high side switching device S3 and a second low side switching device S4. A
third interconnecting pad 56C provides electrical contact between a third high side
switching device S5 and a third low side switching device S6.
[0030] In one embodiment, where the high side switching devices S1, S3, S5 are field effect
transistors (FETs), each device has three terminals including a drain terminal 58A,
58B, 58C, a source terminal 60A, 60B, 60C, and a gate terminal 62A, 62B, 62C. The
drain terminals 58A, 58B, 58C of the high side switching devices S1, S3, S5 may be
connected to the power supply conductive pad 54. The source terminals 60A, 60B, 60C
may be connected to the interconnecting pads 56A, 56B, 56C. And, the gate terminals
62A, 62B, 62C may be electrically connected to a controller 38 (not shown) for control
purposes.
[0031] The low side switching device S2, S4, S6 may be connected to the current sensor 26
by a set of conductive paths 76 through a common conductive pad 64. Here, the common
conductive pad 64 may be part of a first conductive copper layer 78 of the printed
circuit board 50 between the low side switching devices S2, S4, S6 and the current
sensor 26. In an embodiment where the low side switching devices S2, S4, S6 are field
effect transistors (FETs), each device has three terminals including a drain terminal
68A, 68B, 68C, a source terminal 70A, 70B, 70C, and a gate terminal 72A, 72B, 72C.
The drain terminals 68A, 68B, 68C of the high side switching devices S2, S4, S6 may
be connected to the interconnecting pads 56A, 56B, 56C. The source terminals 70A,
70B, 70C may be connected to the common conductive pad 64. And, the gate terminals
72A, 72B, 72C may be electrically connected to a controller 38 (not shown) for control
purposes.
[0032] The low side switching device S2, S4, S6 (through the current sensor 26) may be connected
to the negative terminal 32 of the power source 22 through a conductive pad 66. Alternatively,
the current sensor 26 may be connected to ground through the same conductive pad 66.
The connection to the negative terminal 32, or ground connection, may be fed through
multiple layers in the printed circuit board. This, again, may be important if the
current required to drive the three-phase power device is relatively high. The multiple
layers may be electrically tied together through vias (not shown).
[0033] Each switching device within a set is complimentary to the other switch within the
same set. For example, as mentioned above, when the high side switching device S1
of the first set of switching devices S1, S2 is closed, the corresponding low side
switching device S2 within the first set of switching devices S1, S2 is open. Similarly,
when the high side switching device S1 of the first set of switching devices S1, S2
is open, the corresponding low side switching device S2 within the first set of switching
devices S1, S2 is closed.
[0034] By having complementary switching devices, the opening and closing of switching devices
within each set allows each phase winding A, B, C of the motor 28 to be connected
to a positive terminal 30 or a negative terminal 32 (or ground) of the power supply
22. This is accomplished by having a first terminal 74A connected between the first
high side switching device S1 and the first low side switching device S2, a second
terminal 74B connected between the second high side switching device S3 and the second
low side switching device S4, and a third terminal 74C connected between the third
high side switching device S5 and the third low side switching device S6. The terminals
74A, 74B, 74C permit a voltage V
a, V
b, or V
c to be applied to a corresponding phase winding A, B, or C of the motor 28, respectively.
The current flowing through each phase winding A, B, or C is represented in FIG. 1
by a corresponding variable i_a, i_b, or i_c, respectively.
[0035] The layout of the connection between the positive terminal 30 of the power source
22 and the high side switching devices S1, S3, S5 and the connection between the current
sensor 26 and the negative terminal 32 of the power source 22 (or ground) should be
highly symmetric and balanced, both physically and electrically. However, in a printed
circuit board layout, it is not possible to make the connection between the low side
switching devices S2, S4, S6 and the current sensor 26 geometrically symmetric. Moreover,
the connection between the low side switching devices S2, S4, S6 themselves are not
geometrically symmetric. One aspect of the present invention, as described further
below, is directed to mechanisms in making these connections electrically symmetric
and balanced to avoid problems associated with torque ripple harmonics.
[0036] In the design layout shown in FIG. 4, the physical distance between the source terminal
70A of the first low side switching device S2 and the current sensor 26 is greater
than the physical distance between the source terminal 70B of the second low side
switching device S4 and the current sensor 26. Also, the physical distance between
the source terminal 70C of the third low side switching device S6 and the current
sensor 26 is greater than the physical distance between the source terminal 70B of
the second low side switching device S4 and the current sensor 26. Left with only
the common conductive pad 64 as the electrically connecting member, it has been found
that unacceptable torque ripple harmonics will occur during the operation of a three-phase
power device.
[0037] To solve this problem, in one embodiment, a first set of vias 80 and a second set
of conductive paths 86 in an embedded second conductive copper layer 88 of the printed
circuit board 50 (as shown in FIG. 5) are added to the design. Moreover, the distance
between the source terminal 70A of the first low side switching device S2 and the
current sensor 26 is set to about twice the distance between the source terminal 70B
of the second low side switching device S4 and the current sensor 26. Moreover, the
distance between the source terminal 70A of the first low side switching device S2
and the current sensor 26 is set to about twice the distance between the source terminal
70B of the second low side switching device S4 and the current sensor 26.
[0038] The physical distances between the low side switching devices S2, S4, S6 and the
current sensor 26 are directly proportional to circuit resistance and impedance. In
the printed circuit board layout in FIG. 4, with only the common conductive pad 64,
the voltage loss associated with the second low side switching device S4 would be
less than the losses associated with the first and third low side switching devices
S2, S6. The addition of the first set of vias 80 and the second conductive paths 86
in the second layer 88 of the printed circuit board 50 (as shown in FIG. 5) provides
a more balanced set of electrical paths between the low side switching devices S2,
S4, S6 and the current sensor 26. The first set of vias 80 stitches, or otherwise
connects, the first layer 78 to the second layer 88. The first set of vias 80 should
be placed at unique points or regions as shown in FIGS. 4-5. These points or regions
are in proximity of the first low side switching device S2, the third low side switching
device S6, and the current sensor 26.
[0039] Referring to FIG. 5, in effect, the use of the first set of vias 80 adds a second
parallel current path between first low side switching device S2 and the current sensor
26 and between the third low side switching device S6 and the current sensor 26. This
design helps eliminate, or at least substantially reduce, the effect of torque ripple
harmonics.
[0040] Referring to the design layout in FIG. 6, the common conductive pad 64 also provides
a first set of conductive paths 77 in the first layer 78 of the printed circuit board
50 when current is fed between the low side switching devices S2, S4, S6 themselves.
It is noted that the physical distance between the source terminal 70A of the first
low side switching device S2 and the source terminal 70C of the third low side switching
device S6 is greater than the physical distance between the source terminal 70A of
the first low side switching device S2 and the source terminal 70B of the second low
side switching device S4. Also, the physical distance between the source terminal
70C of the third low side switching device S6 and the source terminal 70A of the first
low side switching device S2 is greater than the physical distance between the source
terminal 70C of the third low side switching device S6 and source terminal 70B of
the second low side switching device S4. Again, left with only the common conductive
pad 64 as the electrically connecting member, it has been found that unacceptable
torque ripple harmonics will occur during the operation of a three-phase power device.
[0041] To solve this problem, in one embodiment, a second set of vias 90 and a third set
of conductive paths 97 in an embedded third conductive copper layer 98 of the printed
circuit board 50 (as shown in FIG. 7) are added to the design. Moreover, the distance
between the source terminal 70A of the first low side switching device S2 and source
terminal 70C of the third low side switching device S6 is set to about twice the distance
between the source terminal 70A of the first low side switching device S2 and the
source terminal 70B of the second low side switching device S4. Moreover, the distance
between the source terminal 70C of the third low side switching device S6 and the
source terminal 70A of the first low side switching device S2 is set to about twice
the distance between the source terminal 70C of the third low side switching device
S6 and the source terminal 70B of the second low side switching device S4.
[0042] The physical distances between the low side switching devices S2, S4, S6 are directly
proportional to circuit resistance and impedance. In the printed circuit board layout
in FIG. 6, with only the common conductive pad 64, the voltage loss associated with
current between some switching devices would be less than the losses associated between
other switching devices. The addition of the second set of vias 90 and the third conductive
paths 97 in the third layer 98 of the printed circuit board 50 (as shown in FIG. 7)
provides a more balanced set of electrical paths between the low side switching devices
S2, S4, S6. The second set of vias 90 stitches, or otherwise connects, the first layer
78 to the third layer 98. The second set of vias 90 must be placed at unique points
or regions as shown in FIGS. 6-7. These points or regions are in proximity of the
first low side switching device S2 and the third low side switching device S6.
[0043] Referring to FIG. 7, in effect, the use of the second set of vias 90 adds a second
parallel current path between first low side switching device S2 and the third low
side switching device S6. This design helps eliminate, or at least substantially reduce,
the effect of torque ripple harmonics.
[0044] FIG. 8 shows another embodiment where the present invention is applied to the high
side switching devices S1, S3, S5. This embodiment addresses a potential need for
current to funnel evenly out of one power source node, as well as evenly connect to
each other when there are recirculating currents between any two of the switching
devices. Accordingly, FIG. 8 shows a layout of the connection between the positive
terminal 30 of the power source 22 and the high side switching devices S1, S3, S5
through a power source node 166 where the connection is not geometrically symmetric.
An aspect of the present invention, as described further below, is directed to mechanisms
in making these connections electrically symmetric and balanced to avoid problems
associated with torque ripple harmonics.
[0045] In the design layout shown in FIG. 8, the physical distance between a power source
node 166 and the first high side switching device S1 is greater than the physical
distance between the power source node 166 and the second high side switching device
S3. Also, the physical distance between the power source node 166 and the third high
side switching device S5 is greater than the physical distance between the power source
node 166 and the second high side switching device S3. Left with only a common conductive
pad 154 as the electrically connecting member, unacceptable torque ripple harmonics
may occur during the operation of a three-phase power device.
[0046] To solve this problem, in one embodiment, a first set of vias 180 and a second set
of conductive paths 186 in an embedded second conductive copper layer 188 of the printed
circuit board 150 (as shown in FIG. 9) are added to the design. Moreover, the distance
between the source node 166 and the first high side switching device S I is set to
about twice the distance between the source node 166 and the second high side switching
device S3. Moreover, the distance between the source node 166 and the third high side
switching device S5 is set to about twice the distance between the source node 166
and the second high side switching device S3.
[0047] The physical distances between the source node 166 and the high side switching devices
S1, S3, S5 are directly proportional to circuit resistance and impedance. In the printed
circuit board layout in FIG. 8, with only the common conductive pad 154, the voltage
loss associated with the second high side switching device S3 would be less than the
losses associated with the first and third high side switching devices S1, S5. The
addition of the first set of vias 180 and the second conductive paths 186 in the second
layer 188 of the printed circuit board 150 (as shown in FIG. 9) provides a more balanced
set of electrical paths between the source node 166 and the high side switching devices
S1, S3, S5. The first set of vias 180 stitches, or otherwise connects, the first layer
178 to the second layer 188. The first set of vias 180 should be placed at unique
points or regions as shown in FIGS. 8-9. These points or regions are in proximity
of the first high side switching device S1, the third high side switching device S5,
and the source node 166.
[0048] Referring to FIG. 9, in effect, the use of the first set of vias 180 adds a second
parallel current path between the source node 166 and the first high side switching
device S1 and between the source node 166 and the third high side switching device
S5. This design helps eliminate, or at least substantially reduce, the effect of torque
ripple harmonics.
[0049] Referring to the design layout in FIG. 10, the common conductive pad 154 also provides
a first set of conductive paths 177 in the first layer 178 of the printed circuit
board 150 when current is fed between the high side switching devices S1, S3, S5 themselves.
It is noted that the physical distance between the drain terminal 58A of the first
high side switching device S1 and the drain terminal 58C of the third high side switching
device S5 is greater than the physical distance between the drain terminal 58A of
the first high side switching device S1 and the drain terminal 58B of the second high
side switching device S3. Also, the physical distance between the drain terminal 58C
of the third high side switching device S5 and the drain terminal 58A of the first
high side switching device S1 is greater than the physical distance between the drain
terminal 58C of the third high side switching device S5 and drain terminal 58B of
the second high side switching device S3. Again, left with only the common conductive
pad 154 as the electrically connecting member, unacceptable torque ripple harmonics
may occur during the operation of a three-phase power device.
[0050] To solve this problem, in one embodiment, a second set of vias 190 and a third set
of conductive paths 197 in an embedded third conductive copper layer 198 of the printed
circuit board 150 (as shown in FIG. 11) are added to the design. Moreover, the distance
between the drain terminal 58A of the first high side switching device S1 and drain
terminal 58C of the third high side switching device S5 is set to about twice the
distance between the drain terminal 58A of the first high side switching device S1
and the drain terminal 58B of the second high side switching device S3. Moreover,
the distance between the drain terminal 58C of the third high side switching device
S5 and the drain terminal 58A of the first high side switching device S1 is set to
about twice the distance between the drain terminal 58C of the third high side switching
device S5 and the drain terminal 58B of the second high side switching device S3.
[0051] The physical distances between the high side switching devices S1, S3, S5 are directly
proportional to circuit resistance and impedance. In the printed circuit board layout
in FIG. 10, with only the common conductive pad 154, the voltage loss associated with
current between some switching devices would be less than the losses associated between
other switching devices. The addition of the second set of vias 190 and the third
conductive paths 197 in the third layer 198 of the printed circuit board 150 (as shown
in FIG. 11) provides a more balanced set of electrical paths between the high side
switching devices S1, S3, S5. The second set of vias 190 stitches, or otherwise connects,
the first layer 178 to the third layer 198. The second set of vias 190 must be placed
at unique points or regions as shown in FIGS. 10-11. These points or regions are in
proximity of the first high side switching device S1 and the third high side switching
device S5.
[0052] Referring to FIG. 11, in effect, the use of the second set of vias 190 adds a second
parallel current path between first high side switching device S1 and the third high
side switching device S5. This design helps eliminate, or at least substantially reduce,
the effect of torque ripple harmonics.
[0053] What has been described is an improved procedure for implementing a switching circuit
and current sensor on a printed circuit board for three-phase power devices. The above-described
system provides a way to optimize, or otherwise balance, the resistive and reactive
impedances in the system. In particular, the printed circuit board has multiple conductive
paths in embedded layers that serve as directional impedance control channels. This
balance helps eliminate, or substantially reduce, the effects of torque ripple harmonics.
The design is particularly important in automotive applications where a balanced system
is needed to provide power to a three-phase motor for power steering. The present
invention solves undesirable oscillations that may occur when a driver is turning
the steering wheel.
[0054] The above description of the present invention is intended to be exemplary only and
is not intended to limit the scope of any patent issuing from this application. For
example, the present discussion used a three-phase motor for automobile applications.
The present invention is also applicable to other three-phase devices where pulse
width modulation is used. The present invention is intended to be limited only by
the scope of the following claims.
1. A printed circuit board for a three-phase power device, the printed circuit board
having at least a first switching device, a second switching device, a third switching
device, and a common source node that are each mounted to a surface of the printed
circuit board, the printed circuit board comprising:
a first set of conductive paths in a first layer of the printed circuit board that
provides electrical conductivity between the common source node, the first switching
device, the second switching device, and the third switching device;
a second set of conductive paths in a second layer of the printed circuit board that
provides electrical conductivity between the common source node, the first switching
device, and the third switching device; and
a plurality of vias that connect the first layer of the printed circuit board to the
second layer of the printed circuit board wherein said plurality of vias are placed
in proximity of the first switching device, the third switching device and the common
source node;
wherein a distance between the common source node and the first switching device and
a distance between the common source node and the third switching device is greater
than a distance between the common source node and the second switching device.
2. The printed circuit board of claim 1 further comprising:
a third set of conductive paths in a third layer of the printed circuit board that
provides electrical conductivity between the first switching device and the third
switching device; and
a second plurality of vias that connect the first layer of the printed circuit board
to the third layer of the printed circuit board.
3. The printed circuit board of claim 2 wherein a portion of the second plurality of
vias is the same as the first plurality of vias.
4. The printed circuit board of claim 1 wherein the first switching device is a first
low side switching device, the second switching device is a second low side switching
device, and the third switching device is a third low side switching device.
5. The printed circuit board of claim 4 wherein the common source node comprises a current
sensor.
6. The printed circuit board of claim 4 further having at least a first high side switching
device, a second high side switching device, and a third high side switching device
that are each mounted to a surface of the printed circuit board, the printed circuit
board further comprising:
a first terminal connected between the first high side switching device and the first
low side switching device, the first terminal providing power to a first phase winding
of the three-phase power device;
a second terminal connected between the second high side switching device and the
second low side switching device, the second terminal providing power to a second
phase winding of the three-phase power device; and
a third terminal connected between the third high side switching device and the third
low side switching device, the third terminal providing power to a third phase winding
of the three-phase power device.
7. The printed circuit board of claim 1 wherein the first switching device is a first
high side switching device, the second switching device is a second high side switching
device, and the third switching device is a third high side switching device.
8. The printed circuit board of claim 7 wherein the common source node comprises a power
source node.
9. The printed circuit board of claim 7 further having at least a first low side switching
device, a second low side switching device, and a third low side switching device
that are each mounted to a surface of the printed circuit board, the printed circuit
board further comprising:
a first terminal connected between the first high side switching device and the first
low side switching device, the first terminal providing power to a first phase winding
of the three-phase power device;
a second terminal connected between the second high side switching device and the
second low side switching device, the second terminal providing power to a second
phase winding of the three-phase power device; and
a third terminal connected between the third high side switching device and the third
low side switching device, the third terminal providing power to a third phase winding
of the three-phase power device.
10. The printed circuit board of claim 1 wherein the distance between the common source
node and the first switching device is about twice the distance between the common
source node and the second switching device.
1. Leiterplatte für eine Dreiphasenleistungseinrichtung, wobei die Leiterplatte zumindest
eine erste Schalteinrichtung, eine zweite Schalteinrichtung, eine dritte Schalteinrichtung
und einen gemeinsamen Quellknoten aufweist, die alle auf einer Oberfläche der Leiterplatte
befestigt sind, wobei die Leiterplatte enthält:
einen ersten Satz leitfähiger Pfade in einer ersten Schicht der Leiterplatte, die
eine elektrische Leitfähigkeit zwischen dem gemeinsamen Quellknoten, der ersten Schalteinrichtung,
der zweiten Schalteinrichtung und der dritten Schalteinrichtung bereitstellt;
einen zweiten Satz leitfähiger Pfade in einer zweiten Schicht der Leiterplatte, die
eine elektrische Leitfähigkeit zwischen dem gemeinsamen Quellknoten, der ersten Schalteinrichtung
und der dritten Schalteinrichtung bereitstellt; und
eine Vielzahl von Kontaktlöchern, die die erste Schicht der Leiterplatte mit der zweiten
Schicht der Leiterplatte verbindet, wobei die Vielzahl von Kontaktlöchern in der Nähe
der ersten Schalteinrichtung, der dritten Schalteinrichtung und des gemeinsamen Quellknotens
angeordnet sind;
wobei eine Entfernung zwischen dem gemeinsamen Quellknoten und der ersten Schalteinrichtung
und eine Entfernung zwischen dem gemeinsamen Quellknoten und der dritten Schalteinrichtung
größer als eine Entfernung zwischen dem gemeinsamen Quellknoten und der zweiten Schalteinrichtung
ist.
2. Leiterplatte gemäß Anspruch 1, ferner enthaltend:
einen dritten Satz leitfähiger Pfade in einer dritten Schicht der Leiterplatte, die
eine elektrische Leitfähigkeit zwischen der ersten Schalteinrichtung und der dritten
Schalteinrichtung bereitstellt; und
eine zweite Vielzahl von Kontaktlöchern, die die erste Schicht der Leiterplatte mit
der dritten Schicht der Leiterplatte verbindet.
3. Leiterplatte gemäß Anspruch 2, wobei ein Teil der zweiten Vielzahl von Kontaktlöchern
mit der ersten Vielzahl von Kontaktlöchern übereinstimmt.
4. Leiterplatte gemäß Anspruch 1, wobei die erste Schalteinrichtung als erster Low-Side-Schalter
ausgebildet ist, die zweite Schalteinrichtung als zweiter Low-Side-Schalter ausgebildet
ist und die dritte Schalteinrichtung als dritter Low-Side-Schalter ausgebildet ist.
5. Leiterplatte gemäß Anspruch 4, wobei der gemeinsame Quellknoten einen Stromsensor
aufweist.
6. Leiterplatte gemäß Anspruch 4, die ferner zumindest einen ersten High-Side-Schalter,
einen zweiten High-Side-Schalter und einen dritten High-Side-Schalter aufweist, die
alle an einer Oberfläche der Leiterplatte befestigt sind, ferner enthaltend:
einen zwischen dem ersten High-Side-Schalter und dem ersten Low-Side-Schalter angeordneten
ersten Abgriff, wobei der erste Abgriff einer ersten Erregerwicklungsphase der Dreiphasenleistungseinrichtung
Energie zuführt;
einem zwischen dem zweiten High-Side-Schalter und dem zweiten Low-Side-Schalter angeordneten
zweiten Abgriff, wobei der zweite Abgriff der zweiten Erregerwicklungsphase der Dreiphasenleistungseinrichtung
Energie zuführt; und
einem zwischen dem dritten High-Side-Schalter und dritten Low-Side-Schalter angeordneten
dritten Abgriff, der einer dritten Erregerwicklungsphase der Dreiphasenleistungseinrichtung
Energie zuführt.
7. Leiterplatte gemäß Anspruch 1, wobei die erste Schalteinrichtung als erster High-Side-Schalter
ausgebildet ist, die zweite Schalteinrichtung als zweiter High-Side-Schalter ausgebildet
ist und die dritte Schalteinrichtung als dritter High-Side-Schalter ausgebildet ist.
8. Leiterplatte gemäß Anspruch 7, wobei der gemeinsame Quellknoten einen Energiequellknoten
enthält.
9. Leiterplatte gemäß Anspruch 7, die ferner zumindest einen ersten Low-Side-Schalter,
einen zweiten Low-Side-Schalter, und einen dritten Low-Side-Schalter aufweist, die
alle an einer Oberfläche der Leiterplatte befestigt sind, wobei die Leiterplatte ferner
aufweist:
einen zwischen dem ersten High-Side-Schalter und dem ersten Low-Side-Schalter angeordneten
ersten Abgriff, wobei der erste Abgriff einer ersten Erregerwicklungsphase der Dreiphasenleistungseinrichtung
Energie zuführt;
einem zwischen dem zweiten High-Side-Schalter und dem zweiten Low-Side-Schalter angeordneten
zweiten Abgriff, wobei der zweite Abgriff einer zweiten Erregerwicklungsphase der
Dreiphasenleistungseinrichtung Energie zuführt; und
einem zwischen dem dritten High-Side-Schalter und dritten Low-Side-Schalter angeordneten
dritten Abgriff, wobei der dritte Abgriff einer dritten Erregerwicklungsphase der
Dreiphasenleistungseinrichtung Energie zuführt.
10. Leiterplatte gemäß Anspruch 1, wobei die Entfernung zwischen dem gemeinsamen Quellknoten
und der ersten Schalteinrichtung etwa der doppelten Entfernung zwischen dem gemeinsamen
Quellknoten und der zweiten Schalteinrichtung beträgt.
1. Carte à circuit imprimé pour dispositif de puissance à courant triphasé, la carte
à circuit imprimé ayant au moins un premier dispositif de commutation, la carte à
circuit imprimé ayant au moins un premier dispositif de commutation, un second dispositif
de commutation, un troisième dispositif de commutation, et un noeud source commun
qui sont montés individuellement sur une surface de la carte à circuit imprimé, la
carte à circuit imprimé comprenant :
- un premier ensemble de conducteurs dans une première couche de la carte à circuit
imprimé qui fournit une conductivité électrique entre le noeud source commun, le premier
dispositif de commutation, le second dispositif de commutation et le troisième dispositif
de commutation ;
- un second ensemble de conducteurs dans une seconde couche de la carte à circuit
imprimé qui fournit une conductivité électrique entre le noeud source commun, le premier
dispositif de commutation et le troisième dispositif de commutation ; et
- une pluralité de trous d'interconnexion qui relient la première couche de la carte
à circuit imprimé à la seconde couche de la carte à circuit imprimé, dans laquelle
ladite pluralité de trous d'interconnexion sont placées à proximité du premier dispositif
de commutation, du troisième dispositif de commutation et du noeud source commun ;
dans laquelle la distance entre le noeud source commun et le premier dispositif de
commutation et une distance entre le noeud source commun et le troisième dispositif
de commutation est supérieure à une distance entre le noeud source commun et le second
dispositif de commutation.
2. Carte à circuit imprimé selon la revendication 1 comprenant en outre :
- un troisième ensemble de conducteurs dans une troisième couche de la carte à circuit
imprimé qui fournit une conductivité électrique entre le premier dispositif de commutation
et le troisième dispositif de commutation ; et
- une seconde pluralité de trous d'interconnexion qui relient la première couche de
la carte à circuit imprimé à la troisième couche de la carte à circuit imprimé.
3. Carte à circuit imprimé selon la revendication 2 dans laquelle une partie de la seconde
pluralité de trous d'interconnexion est la même que la première pluralité de trous
d'interconnexion.
4. Carte à circuit imprimé selon la revendication 1 dans laquelle le premier dispositif
de commutation est un premier dispositif de commutation côté basse tension, le second
dispositif de commutation est un second dispositif de commutation côté basse tension,
et le troisième dispositif de commutation est un troisième dispositif de commutation
côté basse tension.
5. Carte à circuit imprimé selon la revendication 4 dans laquelle le noeud source commun
comprend un capteur de courant.
6. Carte à circuit imprimé selon la revendication 4 ayant en outre au moins un premier
dispositif de commutation côté haute tension, un second dispositif de commutation
côté haute tension, et un troisième dispositif de commutation côté haute tension qui
sont montés individuellement sur une surface de la carte à circuit imprimé, la carte
à circuit imprimé comprenant :
- un premier terminal relié entre le premier dispositif de commutation côté haute
tension et le premier dispositif de commutation côté basse tension, le premier terminal
fournissant du courant à un premier enroulement de phase du dispositif de puissance
à courant triphasé ;
- un second terminal relié entre le second dispositif de commutation côté haute tension
et le second dispositif de commutation côté basse tension, le second terminal fournissant
du courant à un second enroulement de phase du dispositif de puissance à courant triphasé
; et
- un troisième terminal relié entre le troisième dispositif de commutation côté haute
tension et le troisième dispositif de commutation côté basse tension, le troisième
terminal fournissant du courant à un troisième enroulement de phase du dispositif
de puissance à courant triphasé.
7. Carte à circuit imprimé selon la revendication 1 dans laquelle le premier dispositif
de commutation est un premier dispositif de commutation côté haute tension, le second
dispositif de commutation est un second dispositif de commutation côté haute tension,
et le troisième dispositif de commutation est un troisième dispositif de commutation
côté haute tension.
8. Carte à circuit imprimé selon la revendication 7 dans laquelle le noeud source commun
comprend un noeud source de puissance.
9. Carte à circuit imprimé selon la revendication 7 ayant en outre au moins un premier
dispositif de commutation côté basse tension, un second dispositif de commutation
côté basse tension, et un troisième dispositif de commutation côté basse tension qui
sont montés individuellement sur une surface de la carte à circuit imprimé, la carte
à circuit imprimé comprenant :
- un premier terminal relié entre le premier dispositif de commutation côté haute
tension et le premier dispositif de commutation côté basse tension, le premier terminal
fournissant du courant à un premier enroulement de phase du dispositif de puissance
à courant triphasé ;
- un second terminal relié entre le second dispositif de commutation côté haute tension
et le second dispositif de commutation côté basse tension, le second terminal fournissant
du courant à un second enroulement de phase du dispositif de puissance à courant triphasé
; et
- un troisième terminal relié entre le troisième dispositif de commutation côté haute
tension et le troisième dispositif de commutation côté basse tension, le troisième
terminal fournissant du courant à un troisième enroulement de phase du dispositif
de puissance à courant triphasé.
10. Carte à circuit imprimé selon la revendication 1 dans laquelle la distance entre le
noeud source commun et le premier dispositif de commutation correspond à environ deux
fois la distance entre le noeud source commun et le second dispositif de commutation.